This invention relates generally to a precompression pump sprayer wherein spray discharge is valve controlled in dependence upon a build up of pressure in the pump chamber. More particularly, the pump sprayer of the invention has a stationary discharge orifice and a pump priming feature according to which unwanted air is expelled from the pump chamber through the discharge. And, the present pump sprayer has a positive container vent valving feature in which the vent valve is controlled upon impact by the plunger during plunger actuation.
Precompression pump sprayers of the general class to which the present invention is directed are known to operate in response to a build up of pressure in the pump chamber to effect discharge valve opening, the discharge valve being closed by a return spring when the internal pressure is overcome by the force of the spring. A separate return spring can be provided for that member carrying the discharge valve, in addition to another spring provided for returning the plunger to its upstroke or inactive position. The subatmospheric pressure in the pump chamber effected during the plunger upstroke causes product to be suctioned into the chamber.
U.S. Pat. No. 4,941,595 discloses a pump sprayer having such separate springs enabling the discharge valving to be tailored to products of diverse viscosities allowing for different recovery speeds or conditions and permitting the degree of precompression to be adjusted separately. The present pump sprayer likewise has such separate return springs--one for returning the discharge valve and the other for returning the pump plunger towards its upstroke position.
The need arises to provide a precompression pump sprayer having a fixed discharge orifice such that during pumping the spray orifice remains stationary enabling the user to concentrate the discharged product toward a fixed target unlike that of many pump sprayers in which the discharge orifice reciprocates with plunger reciprocation.
It is also well known that any air within the pump chamber of any pump sprayer must be evacuated before the pump sprayer is able to dispense liquid product. The air initially within the pump chamber is merely elastically compressed on the downward plunger stroke, without attaining a sufficiently high pressure to shift the discharge valve open as intended for such pump operation. Thus, when the plunger is released, the air decompresses and a volume of liquid only in proportion to the small amount of air that has been released is suctioned into the chamber. It may therefore become necessary to actuate the plunger several times to achieve pump priming.
A wide variety of pump priming approaches have been taken for evacuating the unwanted air from the pump chamber; for example, downwardly through the dip tube and into the container, as disclosed in U.S. Pat. No. 4,051,983; or by directing the air upwardly and around the pump piston and into the container through a side port located in the pump cylinder wall and/or outwardly to the atmosphere, as disclosed in U.S. Pat. No. 5,064,105.
As an alternative, it is desirable for the air to be evacuated from the pump chamber through the discharge such that any product mixed with air exits the pump through the established discharge path.
It is further known to provide the pump sprayer package with some type of container vent for admitting air into the container to replace the volume of liquid dispensed to avoid hydraulic lock and container collapse. Passive systems have been developed such as those having a resilient flap valve covering the vent port and opening in response to a differential pressure acting on opposite sides of the flap. Active vent systems have been developed providing for the uncovering of the vent port during the pumping operation by mechanically pushing the vent valve open utilizing some element of the pump structure. U.S. Pat. No. 5,244,126 discloses an example of such an active vent valving system for a trigger sprayer.